Spouts connectable to liquid containers are known in the art. It is also known to decant defined volumes by using a measuring device, such as a measuring beaker which is filled to a desired level for measuring a defined volume of the liquid out of a tank or the like. In this manner it is possible to measure aggressive liquids, such as poisonous liquids, caustic or etching liquids, and any other non-toxic liquids in a required manner. The measuring of liquids with a calibrated beaker is acceptable for laboratory operations or devices in which such measuring beakers are readily available. However, the decanting and using of measured volumes of liquids under other conditions where proper measuring devices are not readily available, provides substantial difficulties. For example, the precise measuring and decanting of liquid plant protection chemicals, detergents, fertilizers, food stuffs, and the like pose substantial difficulties with presently available decanting devices. Similar considerations apply to the refueling of the relatively small fuel tanks of small gasoline engines which are quickly over-filled so that spilling occurs. Thus, in many of these instances it is difficult to decant a precise liquid quantity or volume and frequently, it is not possible to precisely follow the directions for the use of the particular liquid, for example for diluting a plant protection chemical or for measuring of precise ingredients.
U.S. Pat. No. 3,556,353 discloses a pump mechanism for the exact decanting of a flowable liquid. In this reference the pump mechanism is attachable to the neck of a bottle and comprises a decanting spout made of glass provided with a cylinder bore in which a glass piston is received for an axial back and forth movement. The known pumping mechanism includes two ball valves, one of which is arranged in a restriction at the lower end of the cylinder bore, while the other ball valve is positioned in a through-bore at the lower end of the glass piston. The two ball valves assure or establish the suction and pressure conditions occurring during pumping so that while pulling the glass piston, liquid is sucked into a defined volume and so that while pushing the glass piston downwardly, the measured liquid is discharged into a connecting pipe. Thus, the measured volume depends on the stroke and a scale indicates the discharged volumes. Such a device is not very practical for use outside a laboratory.